In the storage of perishable items such as food, there are typically two types of environments which are most frequently utilized, namely, coolers and freezers. This is true for refrigeration systems in the home which incorporate a cooler section and a freezer section as separate compartments of the refrigerator, and it is also true for commercial and scientific refrigeration, which will typically utilize compartments such as reach-in coolers and freezers and walk-in coolers and freezers for storage of perishables. Oftentimes, systems such as reach-in coolers and freezers will incorporate refrigeration, control and monitoring systems which are specific to the compartment being operated and monitored, as the compartment is self-contained and its function is clearly defined by its design. However, walk-in coolers and freezers are not so clearly defined, as they may vary greatly, depending on the size, the configuration and the intent of the refrigerated compartment. As a result, walk-in refrigerators and freezers often utilize separate and independent monitoring devices, also known as temperature alarms, as a means of protecting the perishables contained therein in the event of a refrigeration malfunction or failure or in the event of user negligence. Temperature alarms may also be utilized on reach-in compartments that do not provide self-contained monitoring systems for the same purpose.
The design and operation of temperature alarms are fairly standardized and well documented. The typical temperature alarm will utilize a mechanical device such as a thermostat or an electronic device such as a thermistor to sense the temperature of the monitored compartment. It will also provide a method for establishing a temperature limit, also referred to as a setpoint, which the temperature in the compartment should not exceed for a prolonged period of time if the compartment is operating normally. Most frequently, the setpoint will be a high limit, as the most common concern is with perishables spoiling due to refrigeration malfunction because the compartment is too warm. However, a means of establishing a low temperature setpoint as well is often provided to protect against conditions such as freezing of product in a cooler if the temperature gets too cold. Another capability commonly found in temperature alarms is the provision of a time delay. This time delay may be mechanical or electronic in its design and it may be fixed or variable in its delay time. The purpose of the time delay is to override normal rises in compartment temperature that would occur as a result of normal usage. One such normal usage would be doors being left open for a period of time, particularly for loading and unloading of a compartment. Another cause for normal rises in compartment temperature would be a refrigeration system function known as a defrost cycle. Defrost cycles are typically timed occurrences which occur at regular intervals, as dictated by a timer which is integrated into the refrigeration control system.
In a typical defrost cycle, refrigeration is temporarily turned off, while simultaneously, heating elements, placed on the evaporator coil inside of the refrigeration compartment, are turned on. The purpose of the defrost cycle is to melt any ice that may have accumulated on the evaporator coil in the run time since the prior defrost cycle had occurred. This in an important function, as accumulated ice can block the flow of air through the refrigeration coils inside of the evaporator coil, thus affecting the efficiency and performance of the refrigeration system. In a temperature alarm, the interaction of the setpoint and time delay is as follows: Setpoints and a time delay appropriate to the operation of the refrigerator or freezer are manually selected. If the compartment temperature reaches or exceeds a selected setpoint indicating possible abnormal operation, the selected time delay is initiated. If the monitored temperature returns to the safe range before the time delay expires, then the timer is shut off and is reset and no alarm condition is annunciated. This is typically what happens when either of the above described normal operational conditions occurs. If, however, due to negligence or due to an actual malfunction, the temperature exceeds the setpoint for the length of the time delay or longer, then an alarm condition is annunciated so as to alert personnel to the fact that perishables may be in danger of damage or spoilage. This annunciation is typically in the form of a buzzer such as a piezo type device, as well as LED's (light emitting diodes) or other lighting devices or displays which are incorporated into the temperature alarm for this purpose. Oftentimes, a relay or other means of generating a signal is also incorporated into a temperature alarm for the purpose of remote notification of a problem when a facility is unmanned. Temperature alarms, particularly if they are electronic, may also provide a digital readout which will be utilized to display compartment temperatures and other operational parameters. Finally, temperature alarms will also typically provide devices such as reset switches so that a user can respond to an alarm condition.
As mentioned in the prior description regarding setting up of the temperature alarm for a given application, it is stated that setpoints are normally manually selected so that they are correct in accordance with the application, and this represents a shortcoming for the following reasons: It frequently occurs, particularly in new construction and installations, where refrigeration equipment such as walk-ins, and monitoring systems such as temperature alarms, are installed before AC power is available in a given facility. Lack of power makes it impossible to manually adjust operating parameters of the monitoring devices, and when power does become available, the personnel who installed these devices and would have performed these adjustments are often no longer present. The outcome of this scenario is that proper adjustment of the alarms is often overlooked, and they are, therefore, not set up for the application when power is turned on. The result of this shortcoming is often false alarms, which frequently require costly service calls to address and correct the problem, or the even more detrimental outcome of an actual loss of perishables, due either to user negligence such as leaving a door open or due to an actual refrigeration malfunction, because the monitoring system has not been set up properly. Another common problem is that installation instructions are often misplaced, or installing personnel do not want to take the time to read them. Again, the same result is produced with the same consequences.
It is, therefore, desirable to have a monitoring system which, when powered up, has firstly, the capability of detecting the nature of the compartment that is being monitored as to whether it is a cooler or a freezer, and has secondly, the capability of either maintaining its operating parameters or changing its operating parameters, depending on the nature of the monitored environment, both parameter choices from pre-programmed parameter settings, so that the monitoring device is automatically self- adjusting for the application.